Support ring with masked edge

ABSTRACT

A support ring for semiconductor processing is provided. The support ring includes a ring shaped body defined by an inner edge and an outer edge. The inner edge and outer edge are concentric about a central axis. The ring shaped body further includes a first side, a second side, and a raised annular shoulder extending from the first side of the ring shaped body at the inner edge. The support ring also includes a coating on the first side. The coating has an inner region of reduced thickness region abutting the raised annular shoulder.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. provisional patent applicationSer. No. 61/922,451, filed Dec. 31, 2013, which is herein incorporatedby reference.

FIELD

Aspects of the present invention relate generally to devices used tosupport substrates and methods for forming such devices. Moreparticularly, embodiments of the present invention relate to a supportring to support an edge ring in a thermal processing chamber.

BACKGROUND

In the processing of substrates, such as semiconducting wafers, asubstrate is placed on a support in a processing chamber while suitableprocessing conditions are maintained in the processing chamber. A rapidthermal processing (RTP) chamber may be used to heat the substrate withlamps disposed below the substrate. For example, a substrate could berapidly heated to an elevated temperature within a temperature range of250° C. to 1,350° C. During a thermal process, a substrate may besupported by a supporting structure, such as an edge ring, around theedge region of the substrate. The edge ring may be supported by anothersupporting structure, such as a support ring.

The edge ring and support ring are constructed of materials that canwithstand numerous cycles of being rapidly heated and cooled. Quartz(e.g., amorphous silica) is a material often used for the support ringstructure. When heating a substrate from below with lamps in a RTPchamber, it is typically desirable to block lamp radiation from enteringthe area above the substrate in the RTP chamber. Radiation sensors thatare sensitive to radiation emitted by the substrate, such as pyrometers,are often used in the area above the substrate. Preventing lampradiation from entering the area above the substrate prevents radiationfrom hampering performance of the temperature sensors. Because quartz istransparent to light and infrared energy, the upper surface of a quartzsupport ring is often coated with a material, such as silicon, to renderit opaque to the lamp radiation.

Quartz support rings coated with silicon begin to develop cracks in theradial direction after being repeatedly heated and cooled. The cracksmay begin to develop after only a few heating cycles. The crackseventually make the quartz support rings coated with silicon unusable,and frequent replacement of support rings is not cost effective.

Therefore, a need exists for improved quartz support rings having opaquecoatings.

SUMMARY

In one embodiment, a support ring for semiconductor processing isprovided. The support ring includes a ring shaped body with an inneredge and an outer edge, wherein the inner edge and outer edge areconcentric about a central axis. The ring shaped body further includes afirst side, a second side, and a raised annular shoulder extending fromthe first side of the ring shaped body at the inner edge. The supportring also includes a coating on the first side, the coating having aninner region of reduced thickness region abutting the raised annularshoulder.

In another embodiment, a support ring for semiconductor processing isprovided. The support ring includes a ring shaped body with an inneredge and an outer edge, wherein the inner edge and outer edge areconcentric about a central axis. The ring shaped body further includes afirst side and a second side. The support ring also includes a coatingon the first side, the coating having an outer radiation blocking regionof uniform thickness and an inner region of reduced thickness configuredto support an edge ring.

In another embodiment a method for coating a ring shaped body in adeposition chamber is provided. The method includes providing the ringshaped body to the deposition chamber, the ring shaped body having aninner edge and an outer edge, wherein the inner edge and the outer edgeare concentric about a central axis, and a first side and a second side,placing a mask over the first side at the inner edge, wherein a distancebetween the mask and the first side is less than about 500 microns, andforming a coating on the first side, wherein the mask reduces thethickness of the coating on the first side under the mask.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a sectional view of a support ring according to one embodimentof the present invention.

FIG. 2A is a sectional view of a ring shaped body and a mask used tocreate one embodiment of the present invention.

FIG. 2B is a sectional view of a support ring having a coating accordingto one embodiment of the present invention.

FIG. 3A is a sectional view of a ring shaped body and a tapered maskused to create one embodiment of the present invention.

FIG. 3B is a sectional view of a support ring with a tapered coatingaccording to one embodiment of the present invention.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in oneembodiment may be beneficially utilized on other embodiments withoutspecific recitation.

DETAILED DESCRIPTION

A support ring with improved durability for repeated heated and cooling,and a method for making such a support ring, are described. The supportrings described herein are resistant to cracking under thermal stressescreated by repeatedly heating to a temperature between about 250° C. andabout 1,350° C. and cooling to an ambient temperature.

FIG. 1 is a sectional view of a support ring 100 according to oneembodiment. The support ring 100 is configured to support an edge ring160 in a thermal processing chamber (not shown). The edge ring 160 isused to support a substrate 150 that can be processed inside thechamber. Generally, the support ring 100 is disposed on a chambercomponent, such as cylinder 170.

The support ring 100 includes a ring shaped body 110. The ring shapedbody 110 may be defined by an inner edge 112 and an outer edge 114,wherein the inner edge 112 and outer edge 114 may be concentric about acentral axis of the ring shaped body 110. The ring shaped body 110further includes a first side 116, a second side 118, and a raisedannular shoulder 120 extending from the first side 116 of the ringshaped body 110 at the inner edge 112. The support ring 100 alsoincludes a coating 140 on the first side 116, the coating 140 having anouter region of uniform thickness 144 and an inner region of reducedthickness 142 abutting the raised annular shoulder 120. The outer regionof uniform thickness 144 extends radially outward beyond the innerregion of reduced thickness 142. The outer region of uniform thickness144 is thicker than the inner region of reduced thickness 142. The outerregion of uniform thickness 144 and the inner region of reducedthickness 142 could be ring shaped. The inner region of reducedthickness 142 could be configured to support the edge ring 160. Thesupport ring 100 may also include a positioning rim 130 to position thesupport ring 100 on the cylinder 170.

The ring shaped body 110 could be composed of quartz (e.g., amorphoussilica), silicon carbide, silicon oxide (such as amorphous glass),ceramic, or any other heat resistant material. Combinations of suchmaterials may also be used.

The coating 140 could be composed of silicon, which may have anyconvenient morphology, such as polysilicon, monocrystalline silicon,microcrystalline silicon, nanocrystalline silicon, amorphous silicon,and the like. The outer region of uniform thickness 144 could be anouter radiation blocking region. A silicon coating of 25 microns or moremay render a coated surface of the support ring 100 opaque towavelengths of radiation in the operating range of one or morepyrometers (not shown) used to measure the temperatures inside aprocessing chamber. The one or more pyrometers could measure thetemperature from above the support ring 100 while a heating source (notshown) could be located below the support ring 100. Opaque means thatthe mean intensity of the radiation in the operating range of thepyrometer passing through the coating 140 from a heating source, such aslamps (not shown) disposed below support ring 100, is at least sixorders of magnitude lower than the incident radiation received by thesupport ring 100 on surfaces, such as second side 118, facing theheating source. Coating 140 could be designed with a thickness and otherproperties to ensure that the radiation passing through coating 140 isat least twelve orders of magnitude lower than the incident radiationreceived by the support ring 100 from the heating source. Using acoating that is opaque to wavelengths at which the pyrometer issensitive ensures that substantially no radiation in that range ofwavelengths coming directly from the heating source reaches the one ormore pyrometers.

The thickness of the coating 140 in the outer region of uniformthickness 144 could be between 25 and 75 microns, such as between about30 microns and about 60 microns, for example 50 microns. In someembodiments, the thickness of the coating 140 in the outer region ofuniform thickness could be between about 50 microns and 500 microns, forexample 150 microns. Although, the thickness of the coating 140 in theouter region of uniform thickness 144 is substantially uniform, it isnot required to be a constant thickness. For example the thickness ofthe outer region of uniform thickness 144 could vary along a radialdimension of support ring 100. The thickness of the coating 140 in theouter region of uniform thickness 144 may be thick enough to make theouter region of uniform thickness substantially opaque to at least somewavelengths of radiation energy directed at the second side 118 of thesupport ring 100 from a heating source. The thickness of the coating 140in the inner region of reduced thickness 142 could be between about 1micron and about 30 microns, such as between about 5 microns and about20 microns, for example 10 microns. The inner region of reducedthickness 142 could also be described as an inner region of minimumthickness.

FIG. 2A shows a sectional view of a mask 210 that can be used to formcoating 140 on the ring shaped body 110. FIG. 2B shows a sectional viewof support ring 100 having the coating 140, which can be formed throughthe use of mask 210. Mask 210 could be ring shaped and includes asupporting surface 212 that can be used to support the mask 210 on theraised annular shoulder 120 during the formation of the coating 140. Themask 210 also includes a masking surface 214 that is used to reduce thethickness of the coating 140 in the inner region of reduced thickness142 during the formation of coating 140. The mask 210 also includes anouter surface 216 that creates a uniform thickness boundary 218 betweenthe inner region of reduced thickness 142 and the outer region ofuniform thickness 144 when the coating 140 is formed.

Referring to FIGS. 1 and 2B, the uniform thickness boundary 218 could beformed at a location where an outer edge of a supporting surface of theedge ring 160 could be supported. If the edge ring 160 is also composedof a radiation blocking material, such as silicon carbide, which may beopaque to some wavelengths or spectra of radiation, substantially all ofthe light and infrared energy radiating from beneath the support ring100 in the thermal processing chamber is blocked or absorbed by thesubstrate 150, the edge ring 160, or the outer region of uniformthickness 144.

Referring to FIGS. 1, 2A and 2B, a method to form coating 140 on ringshaped body 110 could include providing the ring shaped body 110 to adeposition chamber (not shown), placing the mask 210 over the first side116 at the inner edge 112, and forming the coating 140 on the first side116. The mask 210 reduces the thickness of coating 140 on the first side116 that is under the masking surface 214. The distance between themasking surface 214 and the first side 116 could be between about 10microns and about 500 microns, for example about 200 microns. In someembodiments, the distance between the masking surface 214 and the firstside 116 could be between about 1 micron and about 30 microns, such asbetween about 5 microns and about 20 microns, for example 10 microns.

FIG. 3A shows a sectional view of a tapered mask 310 that can be used toform a tapered coating 340 on the ring shaped body 110. FIG. 3B shows asectional view of a support ring 300 having the tapered coating 340,which can be formed through use of tapered mask 310. Tapered mask 310could be ring shaped and includes a tapered mask supporting surface 312that can be used to support the tapered mask 310 on the raised annularshoulder 120 during the formation of the tapered coating 340. Taperedmask 310 is tapered to reduce the thickness of tapered coating 340 astapered coating 340 approaches inner edge 112. The tapered mask 310 alsoincludes a tapered masking surface 314 that is used to reduce thethickness of the tapered coating 340 in a tapering region 342 during theformation of tapered coating 340. The tapered masking surface 314 couldhave a substantially linear slope relative to the first side 116. Thetapered mask 310 also includes an outer surface 316 that creates anouter tapering boundary 318 between the tapering region 342 and an outerregion of uniform thickness 344 when the tapered coating 340 is formed.Thus, the tapering region 342 (i.e., an inner region along the radialdimension of the ring shaped body 110), borders the outer region ofuniform thickness 344 at the outer tapering boundary 318.

The thickness of the tapered coating 340 in the outer region of uniformthickness 344 could have a thickness of between 25 microns and 200microns, for example 60 microns. In some embodiments, the thickness ofthe tapered coating 340 in the outer region of uniform thickness 344could have a thickness of between 200 microns and 500 microns, forexample 400 microns.

The tapered mask 310 could also include a minimum thickness maskingsurface 313 that could be used to create a region of minimum thickness346 abutting the raised annular shoulder 120 when the tapered coating340 is formed. The minimum thickness masking surface 313 could besubstantially parallel to the first side 116 of the ring shaped body 110making the thickness of tapered coating 340 substantially uniform in theregion of minimum thickness 346. Although, the thickness of the taperedcoating 340 in the region of minimum thickness 346 is substantiallyuniform, it is not required to be a constant thickness. For example, thethickness of the tapered coating 340 in the region of minimum thickness346 could vary along a radial dimension of support ring 300. The pointwhere the tapered masking surface 314 meets the minimum thicknessmasking surface 313 creates an inner tapering boundary 320 after thetapered coating 340 is formed. The inner tapering boundary 320 isbetween the tapering region 342 and the region of minimum thickness 346(i.e., the inner region). Thus, the tapered coating 340 tapers from theregion of uniform thickness 344 at the outer tapering boundary 318 tothe reduced or minimum thickness at the inner tapering boundary 320located in the inner region of the ring shaped body 110. The taperedcoating 340 could have an inner thickness substantially equal to theminimum thickness between the inner tapering boundary 320 and the inneredge 112.

The inner tapering boundary 320 could be a first distance from the inneredge 112 of the ring shaped body 110, wherein the first distance couldbe between about 0.1 mm and about 20 mm, such as between about 0.5 mmand about 15 mm, for example about 5 mm. The thickness of the taperedcoating 340 in the region of minimum thickness 346 could be betweenabout 1 micron and about 30 microns, such as between about 5 microns andabout 20 microns, for example 10 microns. The outer tapering boundary318 could be a second distance from the inner edge 112 of the ringshaped body 110, wherein the second distance is between about betweenabout 0.2 mm and about 25 mm, such as between about 0.5 mm and about 20mm, for example about 10 mm. In some embodiments, tapered mask 310 couldreduce the thickness of the tapered coating 340 for a span between 0.1mm and 24 mm along a radial dimension from the central axis, forexample, a span between 0.5 mm and 5 mm.

The thickness of the tapered coating 340 at the inner tapering boundary320 could be between about 1 micron and about 30 microns, such asbetween about 5 microns and about 20 microns, for example 10 microns.The thickness of the tapered coating 340 at the outer tapering boundary318 could be between about 25 microns and about 75 microns, such asbetween about 30 microns and about 60 microns, for example 50 microns.In some embodiments, the thickness of the tapered coating 340 at theouter tapering boundary 318 could have a thickness of between 60 micronsand 500 microns, for example 250 microns.

Referring to FIGS. 1, 3A and 3B, a method to form tapered coating 340could include providing the ring shaped body 110 to a deposition chamber(not shown), placing tapered mask 310 over the first side 116, andforming a tapered coating 340 on the first side 116. The tapered mask310 reduces the thickness of tapered coating 340 on the first side 116that is under the tapered masking surface 314 and the minimum thicknessmasking surface 313. The distance between the tapered masking surface314 and the first side 116 could taper from a first value to a secondvalue, wherein the first value could be between about 300 microns andabout 500 microns, for example 400 microns, and the second value couldbe between about 10 microns and about 200 microns, for example 50microns. In some embodiments, the distance between the tapered maskingsurface 314 and the first side 116 could taper from a first value to asecond value, wherein the first value could be between about 25 micronsand about 75 microns, for example 50 microns, and the second value couldbe between about 1 micron and about 30 microns, for example 10 microns.In some embodiments, the distance between the tapered masking surface314 and the first side 116 could be between 10 microns and 300 microns,for example 50 microns. In some embodiments, the distance between theminimum thickness masking surface 313 and the first side 116 could bebetween 10 microns and 200 microns, for example 60 microns. In someembodiments, the distance between the minimum thickness masking surface313 and the first side 116 could be between be between about 1 micronand about 30 microns, such as between about 5 microns and about 20microns, for example 10 microns.

The first side 116 could be exposed to a silicon precursor material toform the coating 140 or the tapered coating 340. The process forexposing the first side 116 to the silicon precursor material may be aCVD process or a PVD process. In one aspect, a plasma process, such as aplasma spray process or plasma CVD process, may be used. In a plasma CVDprocess, a silicon deposition precursor, such as a silane, for exampletrimethyl silane or disilane, may be provided to a processing chambercontaining the ring shaped body 110 with the mask 210 or the taperedmask 310 positioned thereon. The silicon deposition precursor may beprovided with a plasma forming gas, such as argon or helium. Acapacitive or inductive plasma is formed in the processing chamber, andthe coating 140 ore the tapered coating 340 forms.

Referring to FIG. 1, it has been observed that when a quartz supportring, such as ring shaped body 110, is coated on its upper surface witha silicon layer of substantially uniform thickness and repeatedly heatedto an elevated temperature, such as a temperature of at least 900° C.,cracks begin to form in the radial direction after only a few cycles.The cracks eventually make the support ring unusable. It has also beenobserved that when the same support ring has a silicon coating with aregion of reduced thickness near the inner edge 112, such as the innerregion of reduced thickness 142, and the support ring is repeatedlyheated to elevated temperatures, crack formation is substantiallydelayed or reduced.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

What is claimed is:
 1. A support ring for semiconductor processing,comprising: a ring shaped body comprising: an inner edge and an outeredge, wherein the inner edge and outer edge are concentric about acentral axis; and a first side and a second side, a raised annularshoulder extending from the first side of the ring shaped body at theinner edge; and a coating on the first side, the coating having an innerregion of reduced thickness abutting the shoulder.
 2. The support ringof claim 1, wherein the inner region of reduced thickness is ringshaped.
 3. The support ring of claim 2, wherein the ring shaped bodycomprises quartz.
 4. The support ring of claim 3, wherein the coating ispolysilicon.
 5. The support ring of claim 4, wherein the coating has asan outer region of uniform thickness extending radially outward beyondthe inner region of reduced thickness.
 6. The support ring of claim 5,wherein the thickness of the coating in the outer region is between 30microns and 60 microns, and the thickness of the coating in the innerregion is between 1 micron and 30 microns.
 7. The support ring of claim5, further comprising a tapering region between the outer region andinner region forming an outer tapering boundary between the outer regionand the tapering region and an inner tapering boundary between thetapering region and the inner region, wherein the coating tapers fromthe uniform thickness at outer tapering boundary to the reducedthickness at the inner tapering boundary.
 8. The support ring of claim7, wherein the inner tapering boundary is a first distance from theinner edge and the outer tapering boundary is a second distance from theinner edge, the first distance is between 0.1 mm and 20 mm, and thesecond distance is between 0.2 mm and 25 mm.
 9. The support ring ofclaim 7, wherein the tapering of thickness of the coating in thetapering region has a linear slope.
 10. The support ring of claim 9,wherein the thickness of the coating in the outer region is between 30microns and 60 microns and the thickness of the coating in the innerregion is between 1 micron and 30 microns.
 11. The support ring of claim10, wherein the inner tapering boundary is a first distance from theinner edge and the outer tapering boundary is a second distance from theinner edge, the first distance is between 0.1 mm and 20 mm, and thesecond distance is between 0.2 mm and about 25 mm.
 12. A support ringfor semiconductor processing, comprising: a ring shaped body comprising:an inner edge and an outer edge, wherein the inner edge and outer edgeare concentric about a central axis; and a first side and a second side;and a coating on the first side, the coating having an outer radiationblocking region of uniform thickness and an inner region of reducedthickness configured to support an edge ring.
 13. The support ring ofclaim 12, wherein the inner region borders the outer radiation blockingregion at an outer tapering boundary, the coating thickness tapersradially inward from the uniform thickness at the outer taperingboundary to a minimum thickness at an inner tapering boundary located inthe inner region, and the coating has an inner thickness equal to theminimum thickness between the inner tapering boundary and the inneredge.
 14. The support ring of claim 13, wherein the inner taperingboundary is a first distance from the inner edge and the outer taperingboundary is a second distance from the inner edge, the first distance isbetween 0.1 mm and 20 mm, and the second distance is between 0.2 mm and25 mm.
 15. The support ring of claim 13, wherein the uniform thicknessis between 30 microns and 60 microns and the minimum thickness isbetween 1 micron and 30 microns.
 16. The support ring of claim 12,wherein the inner region of reduced thickness is ring shaped.
 17. Thesupport ring of claim 12, wherein the ring shaped body comprises quartz.18. The support ring of claim 12, wherein the coating is polysilicon.19. The support ring of claim 12, wherein outer radiation blockingregion of uniform thickness extends radially outward beyond the innerregion of reduced thickness.
 20. The supporting ring of claim 12,further comprising a raised annular shoulder extending from the firstside of the ring shaped body at the inner edge, wherein the coatingextends from the outer edge to the raised annular shoulder.